Radiosonde



Patented May 30,1950

RADIOSONDE Leo S. Craig, Eatontown, N. 3., and Leon lilllman. New York,N. Y., assignors to the United States at, America as represented by theSecretary of Application September 6, 19, Serial No. 552,851

1 Claim. (Cl. 177-380) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described hereinmay be manufactured and used byv or for the Government for governmentalpurposes, without the payment to us of any royalty thereon.

This invention relates to meterological apparatus and more particularlyto radiosondes suitable for being carried aloft by a free balloon.During its flight the radiosonde transmits radio signals, which, whenproperly interpreted, give essentially continuous record of pressure,temperature and humidity of the atmosphere through which it passes.

The temperature, humidity and pressure'data is automatically transmittedby means of a modulated carrier, the modulationbeing performed by apredetermined number and sequence of audio frequencies, the sequence ofthe audio fraquencies determining the reading of the instruments.

In the prior art it has been customary to send the meteorological dataeither by means of Morse code signals or by means of a variable audiofrequency, the frequency being varied in a continuous manner. The Morsecode transmitters, as a rule, require expensive apparatus at theradiosonde, and either good knowledge of the Morse code by themonitoring operators or an expensive teletype equipment for recordingthe Morse code messages. The continuous audio frequency method oftransmitting instrument readings requires a rather involved and bulkyreceiving equipment thus again complicating the installation used forobtaining the meteorological data.

According to the first embodiment of the invention, illustrated in Fig.1, simplification of the meteorological data-collecting system isaccomplished by resorting to the use of a limited number of audiofrequencies for modulating the radiosonde transmitter. The frequenciesare arranged in coded combinations, sufiicient number of combinationsbeing provided for obtaining the desiredrange of readings for allinstruments. According to the first embodiment of the invention, theradio frequency of the radiosonde transmitter is modulated by aself-blocking u. h. f. oscillator the blocking frequency of which iscontrolled by varying the resistance in the blocking circuit of theoscillator. The resistance is varied in steps, each step transmitting apredetermined audio frequency, the audio frequency being produced by therate of blocking of the self-blocking U. H. F. oscillator. Suflicientfrequency difference is used between the steps so that the monitoringoperator, who receives the signals over a head-set or a loud speaker,may recognize the particular frequency transmitted without any 2 specialdifficulty, and is in a position to differentiate it from otherfrequenciesused for transmitting the frequency-coded instrumentreadings. The selection of resistances is performed by meteorologicalinstruments, the moving elements of which operate over the commutators,thus interposing suitable resistances in the circuit of the audiooscillator.

According to the first embodiment of the invention the radiosonde,therefore, consists of a battery-energized radio transmitter designed tobe carried aloft by a free balloon, and a plurality of meteorologicallysensitive instruments which introduce different resistances into thecircuit of the self-blocking U. H. F. oscillator-modulator connected tothe radio transmitter, the modulator keying the ultra-high frequency ofthe transmitter by the interrupted U. H. F. of the modulator, theinterrupting rate of the first U. H. F. being used for determining thereadings of the meteorological instruments also carried aloft by thesame-free balloon.

The advantages of the first system reside in a relatively simpleradiosonde transmitter, and what is especially important-simplificationof the receiving equipment, which in its simplest form, reduces to anordinary super-heterodyne receiver with the head phones connected to theoutput of the receiver.

Another important advantage resides in th fact that the monitoringoperators may be trained very readily to record the received data, andneed not be trained to record Morse code messages. Interpretation of theMorse code messages is obviously more difilcult for an untrainedoperator than interpretation of a limited number of audio frequencycombinations which are used by the invention to accomplish the samepurpose. According to the second embodiment of the invention,illustrated in Fig. 2, a phonograph disc is used for transmitting thesignals from the radiosonde, the disc being provided with fourreproducing arms one arm being a reference arm and the remaining threearms being th arms which are operated by the meteorological instruments.The disc is also provided with a sector which bears upon it thecombinations of the recorded audio frequencies which correspond to theaudio frequencies of Fig. 1. The angular position of the reproducingarms with respect to the recorded sector of the disc is controlled bythe meteorological instruments and, therefore, the reproducers transmitdifferent frequency combinations, the transmitted combinations dependingupon the readings of the instruments.

It is, therefore, the principal object of this invention to provide aradiosonde transmitting equipment which transmits meteorological data bymeans of a radio carrier modulated by means of a plurality of audiofrequencies, the audio frequencies being arranged in differentpermutations to indicate the position of meteorologically sensitiveinstruments.

Another object of this invention is to provide a radiosonde themodulating U. H. F. oscillator of which comprises a self-blockingoscillator whose blocking frequency may be controlled by means ofvariableresistances which are selected by the meteorologicalinstruments. The meteorological instruments, therefore, control theblocking frequency of the modulator.

Still another object of this invention is to provide a radiosonde themeteorological instruments of which control the angular positions of thereproducing arms which are in reproducing engagement with a disc. Onesector of said disc has a plurality of audio frequency combinationsrecorded upon it, the reproduced frequencies being used for determiningthe readings of the meteorological instruments.

The novel features which we believe to be characteristic of ourinvention are set forth with particularity in the appended claims, ourinvention itself, however, both as to its organization and method ofoperation, together with the further objects and advantages thereof, maybest be understood by reference to the following description inconnection with the accompanying drawings in which:

Figure. 1 is a schematic diagram of the first type of the radiosondetransmitter, and

Figure 2 is a schematic diagram of the second type of the radiosondetransmitter.

Before proceeding with a more detailed description of the schematicdiagram shown in Fig. 1, it may be helpful to outline briefly thegeneral principles of operation of the device. The

invention is illustrated in connection with three meteorologicalinstruments I44, I49 and I49 which are responsive to humidity,temperature and pressure respectively of the atmosphere surroundingthem. Since all of these instruments are coupled to a singletransmitter-modulator combination I02-I04, it is necessary to providesome automatic switching arrangement for connecting these instruments ina predetermined sequence. This is accomplished by a rotatinginstrument-selecting switch I42 provided with a conducting sector "I andfour conducting segments I05, I09, I99 and I99. Segments I89, I99 andI99 connect the meteorological instruments to the transmitter andsegment I95 connects the transmitter to an auxiliary rotating switch I52which is used for indicating the angular position of the rotatingswitches I59 through I50. By knowing the angular position of therotating switches I59 through I50, the operator is in a position tojudge which particular instrument is transmitting the signals at anygiven time, all rotating switches being rigidly connected through asingle driving shaft to a clock or gravity type driving mechanism I19.Thus the operating cycle of the switches is as follows: it begins withthe sending of a predetermined audio frequency 11 to indicate theangular position of all switches, and it is then followed by thetransmission of signals by the instruments. All switches are procallyconductive lever arms I19, I11, and I10 which connect these arms throughbrushes II I,

II5, III-and throughcommutatorsl",I50, I5I

to one of the six "rotating switches I52 through I58. Depending upon theposition of these arms on the commutators I49, I50, I5I, certain audiofrequency combinations are transmitted by the radiosonde, the values ofthe transmitted frequencies being determined by the values of theresistances I 5I through I12 connected in series with the switches I53through I59. These rotating switches are provided with the rotating armsI14, I15, "6,141, I59, I90, I99, I49, I45, III, III, .I35, I25, I21,I29, II9, I2I, I23, the number of the rotating arms on each switchcorresponding to the number of the instruments used in the radio sonde.These rotating arms are apart on each switch, corresponding to the 90separation of segments I09, I99, I99 of switch I42, thus ensuring thateach of switches I59 to I50 is ready to conduct whenever segment I9Itouches conducting segment I99, I90, or I99 of switch I42. Which of the.six switches will conduct will of course further depend upon thecommutator segment that brushes H3, H5, or ill happen to be touching atany given moment. Thus during one complete revolution of the switchesthe transmitter sends signals which begin with the signal identifyingthe angular position of the switches, and this is followed by threesignals transmitted by the three instruments. each instrument signalconsisting of two different audio frequencies. These audio frequenciesare used for identifying the instrument readings on the radiosonde. Thefunctioning of the modulator-transmitter com- .bination will bedescribed first, and it will be then followed with the description ofconnections between the meteorological instruments and the modulator.

Proceeding now with a more detailed description of the schematicdiagram, an antenna I00 is connected to an ultra-high frequency carrieroscillator I02, the grid of which is connected to a trigger typemodulating oscillator I04. The frequency of the keying circuit isdetermined by the parameters of the grid coil I05, the plate coil I00and the tuning capacitor H0. The oscillating frequency of thisoscillator may be in the order of one megacycle per second. Theoscillation is intermittent, being controlled by theresistancecapacitancecircuit II2--I I 4, and the additional resistancesI50 through I12 which are periodically connected in parallel with theresistance II2 by the meteorologically sensitive instruments I44, I49,I49 and the rotating switches I52 through I58. The audio frequency thatis heard by the monitoring operator at the receiver is determined by thefrequency with which the oscillator I04 is triggered on" and 0111" Thetransmitter thus represents a well known double modulation transmitter.During the oscillating condition of triode I04, the grid takes thepositive charge at half cycles causing a current to flow throughresistance H2, and one of the additional resistances parallelingresistance 2 at various times. The voltage developed across thecondenser-resistance network is applied as a negative biasing voltage tothe grid of triode I04. The magnitude of this biasing voltage is afunction of the charging rate of condenser II4 through the grid-filamentresistance of tube I04; the voltage finally builds up to a sufiicientvalue to block the oscillator. During the non-oscillating condition thecapacitor II4 discharges through the two parallel resistances untilnegative biasing voltage is again sufficiently low to allow the tube tooscillate. This action is repeated cyclically at an audio frequencyrate. The duration of the oscillating period is a function of thecapacitor H4 and the tube parameters, while the duration of thenon-oscillating period is controlled by the capacitor H4 and theresistance network shunting this capacitance. The latter, as mentionedpreviously, is composed of fixed resistance I I2 and of a plurality offixed resistances, I80 through I12, one of which is placed during theoperating cycle in parallel with resistance II2 by the meteorologicalinstruments. Hence by varying the value of the resistance network, as isdone by the meteorological instruments, it is possible to vary theduration of the non-oscillating period of triode I04; i. e., thefrequency at which the short oscillating pulses occur. As mentionedpreviously, it is the frequency of the short oscillating pulses thatactually produces the audio signals at the receiver.

The ultra-high frequency oscillator I02 operates at a frequency whichmay be in the order of 100 megacycles. The frequency of the oscillationis controlled by the grid coil I I6, the plate coil H8, and thegrid-plate capacitance of the triode in parallel with the effectivecapacitance between the leads of the condenser I20. The oscillations ofthis oscillator are also intermittent, being on when the modulatingoscillator is off, and off when the latter is on. This action takesplace as follows: when the modulating oscillator is in an oscillatingcondition the plate of triode I04 draws current and a negative directcurrent voltage appears across the resistor I22 connected in its platesupply circuit. This voltage is applied across the portion I24 of thegrid circuit resistor I26, I24 of the carrier oscillator triode I02through the coupling capacitor I28. The constants of the circuit areadjusted so that this voltage is of sufficient magnitude to block thecarrier oscillator I02, the oscillations beginning again when themodulating oscillator I04 becomes non-oscillating and the voltage acrossthe biasing resistor I22 collapses. Capacitor I30 is a stabilizingcapacitor for the modulating oscillator and condensers I32, I34 and;I36are audio frequency by-pass condensers. Resistor I26 is a stabilizingresistor for the carrier oscillator. 'The output of the carrieroscillator is coupled inductively to the half-wave vertical antenna I bymeans of a loop I3} at the center of the antenna.

From the foregoing description it will be evident that the U. H. F.oscillator I02 is modulated by'oscillator I04 at the frequency ofoscillator I08 and the carrier wave sent out by the transmitter is adouble modulation wave interrupted completely for short periods of time,the value of the resistance inserted by the meteorograph instrumentscontrolling the rate of these interruptions.

The roles played by resistor H2 and the resistances I80 through I12inserted by the meteorograph instruments is as follows: if theresistance introduced by the meteorographs is infinite, resistance II2alone forms the controlling resistance of the oscillator I04. If theresistance connected by the instruments i lower than infinity. the audiofrequency interruptions will be determined by the equivalent resistanceequal to resistor I I2 paralleled by the instrument resistor. Thus anumber of audio frequencies may be generated by merely changing theresistance paralleling the resistance II2. The value of resistance H2 ispreferably such that, with only resistance H2 in the circuit, themodulating frequency is in the order of a few cycles per second so thatit does not produce any audible signals at the receiver. Theadvisability of having resistors H2 in the circuit is obvious. It actsas a stabilizing and biasing resistor in the circuit of the oscillatorI04, thus avoiding floating grid conditions, transients and severe loadsthat may be otherwise imposed occasionally on the power supply and thecurrent carrying capacity of triode I04.

Referring now to the apparatus for connecting the resistances I throughI12 in shunt with resistance II2. The shunting connection isaccomplished over conductors I40, I, the resistors I60 through I12, theswitches I82 through I88. the commutators I48. I60, III, the conductivearms I10, I11, I18, the instruments I44, I48, I48,

and the instrument selector switch 142. The

transmitted by the U. H. F. transmitter I02. The

audio frequencies produced by the resistors are also designated in thedrawing directly over the resistors as frequencies {1 through is signifythe fact that h is used for designating angular position of the switchesand that is through 14 are used in different permutations to designatethe readings of the instruments.

As mentioned previously, each of the switches I53 through I58 consist ofthree rotating arms. such as I14, I15, and I16, which are all mounted onthe same shaft indicated bya dotted line I31, connecting the commonshaft of the rotating arms to the driving mechanism I19 which rotatesthem, the arm I80 of the rotating switch I62, and the instrumentselecting sector I8I of the instrument selector I42 at uniform angularvelocity.

The instrument selector sector I8I and the switch arms I80, I14, I16,I18, etc. are illustrated in the drawing in their normal startingposition. Therefore, at this instant, conductor I40 connects the audiofrequency oscillator I04-to a resistance I 60 which is connected on oneside to ground through a conductor I4 I segment I82. switch arm I80,conductor I84, segment I85, sector I8I. the shaft of sector I 8 I and agrounded conductor I86. Because of this circuit the blocking audiofrequency of the oscillator I04 is determined at this instant by theresistance I80 connected in parallel with resistance II2. Apredetermined audio frequency ii is generated by the oscillator I04, andsince this is the starting position of the system, the appearance ofthis frequency at the receiver immediately notifies the monitoringoperator of the position of all rotating switches as well as of theposition of the rotating sector I8I. For the sake of clarity of thedisclosure specific angles will be assigned to some of the elements ofthe system but it will be obvious to those skilled in the art that thequoted angles may be different. and the invention is not limited to thespecific values given in the specification. Thus the instrumentselecting sector may span a 75 angle, and the conducting segments I82,I88, I81, I88, etc. may each span an angle of 20 separated by an angleof 30. Thus there is an angle of 70' between the leading edge of thesegments and the lagging edge of the second segment, such angulararrangement of the segments insuring completion of the electricalcircuit at the switches I52 through I68. The conducting segments I85,I89, I88 and I88 of switch I 42 are 10 each, thus leaving a 5 clearancebetween them to avoid their shorting .by sector I 8|. 2

From the given description it follows that the oscillator I04 willgenerate blocking frequency fr as long as arm I80 makes contact witheither segment II! or I", and the eight cycle frequency when only theresistance Iii shunts condenser Iii, the latter frequency beinginaudible at the receiver. This signal notifies the monitoring op-verator that the instrument selecting se ment III is leaving segment Illand is on its way toward the conducting segment Ill if a clockwiserotation of the elements, indicatedin the figure, is assumed. Theoperator will thus know that the next s als will be those indicating thereading of the aneroid lit. The latter consists of one or more evacuatedaneroid capsules. whose expansion or contraction is multiplied by anappropriate level system into'a linear or angular motion and it is thisangular motion that is utilized for changing the position of theconducting arm Ill onthecommutaior Ill.

As illustrated in the figure. the number of the commutator segments onthe commutator ill is equal to the number of the rotating switches Illthrough Ill, this latter number being equal to six. Each commutatorsegment is connected by means of'its conductor, conductors as: throughI, to its respective switch. Therefore, when the aneroid operated armill is, for example. on the extreme right segment, it connects conductorill to the upper switch ill, and segment lflwhich is reached by therotating arm I'll approximately at the same time as sector Ill of theinstrument selecting switch lflreaches segment I. That this is actuallythe case may be perceived from the examination of the drawing'where armIll is illustrated as lagging by the leading edge of the sector ill.Thus. resistor ill will control the blocking frequency of the oscillatorI at this instant, the circuit being conductor Ill. resistor Iii,segment Ill, arm Ill, conductor ill, commutator ill, brush ill, aneroidarm will, conductor III. segment lilrsecior ill, and groundedconductor 1. Identical circuits will exist when arm ill reaches segmentill with the resistance I62 shunting resistance Ill and frequencls-appearing at this instant. This notifies the monitoring operator thatthe aneroid arm I" is on the extreme right segment of the commutatorIII. Previous calibration of the aneroid immediately establishes at thereceiver the pressure to which the aneroid bellows are subjected at thisinstant. This cycle repeats itself in connection with the temperatureunit I it and humidit unit I, when the instrument selecting sector Iiimakes contact first with the conducting segment Ill and then segment I.

The operation of the temperature and humidity units (it and I from thepoint of view of the electrical transmission of their positions isobviously identical to the electrical transmission of the position ofthe aneroid. and, therefore needs no additional description. Sufilce itto say that upon the instrument selecting sector ill leaving conductingsegment ill, there will be again an interval of time when the modulatingoscillator I will key the U. H. F. transmitter III at a low blockingfrequency of 8 cycles. thus interposing a period of silence at thereceiver. This period of silence immediately notifies the monitoringoperator that the instrument selector has left the aneroid instrumentand is on its way to the temperature indicator. The same type of silencecycle is used for notifying the monitoring operator that the instrumentselecting segment has left the conducting segment I and is on its way tothe humidity indicator 1.

Figure 2 discloses another suitable arrangement for accomplishing theresults outlined in 8 connection with Fig. 1. In Fig. 3, fourreproducing arms llll through "I are placed on: disc m which is rotatedat a uniform speed means of a mechanical or electrical drive. disc has asector III :which, is slightly elevated above the remaining portion ofthe disc so that the reproducing arms are normally suspended from thepivot points and are not making any contacts with the disc except whenthey come in contact with the elevated segment III of the disc. Thesegment has a plurality of recorded audio frequency permutatiom, therecordings being made in such a manner that one frequency is transmittedfirst, and, after a period of silence,

the other frequency. These frequency permutations are used in the'samemanner as those previously mentioned in-connection with Fig. l. The arms20:, I and I are connected to the pressure, temperature, and humiditelements i I l, I II and lit respectively, these elements determiningthe angular positions of the reproducing arms with respect to therecorded sector of the disc. Accordingly. depending upon the readings ofthe meteorological instruments, the reproducing arms engage differentportions of the sector and transmit different frequency permutations thelatter identifying the instrument readings with the aid of thecalibration charts. Arm Ill lsusedffcr notifying the monitoring operatorof the sequence of rotation of the arms so that he could be apprisedwhich particular arm is transmittingthe signal at any given time. Thearm I. therefore, accomplishes the same function as the rotating switchit! n g. 1. The output signals of the reproducingarms are impressed onthe control grid of the amplifier "Land the output of the latter may beused in any desired manner for modulating the U. H. F. oscillator.Either asingle or double modulation principle of transmission may beused in a well known manner, such as that described in Fig. 1.

The advantage of the arrangement illustrated in Fig. 2, resides in thefact that a larger number of frequency permutations may be used in thisarrangement without unduly overburdening the equipment, and thestructural features are simpler than those used in Fig. l.

What is claimed is:

A radiosonde transmitter for transmitting ma teorological readings byselective combination of transmission frequencies including aself-blocking oscillator, impedance means for determining theself-blocking frequency of said oscillator. said impedance meansincluding a fixed element and selectivel connectable elements shuntingsaid fixed element, said connectable elements comprising a plurality ofsets of parallel resistors, each set of parallel resistors being soarranged as to provide a combination of resistors that diifers inarrangement from that of any other set, a plurality of rotatingswitchesconnected'respectively to said sets of parallel resistors; aplurality of commutators connected to each of said switches, each ofsaid commutators having an adjustable arm; a plurality of meteorologicalinstruments, the number of the instruments corresponding to the numberof said commutators, mechanical connections between said instruments andthe respective commutator arms, whereby the positions of said-commutatorarms correspond to the respective readings of said instruments, aninstrument selecting switch coupled to said sets of parallel resistors.and a driving means connected to said selecting switch and said rotatingswitches, said selecting and rotating switches being so constructed andarranged that only one meteorological instrument is connected to saidoscillator at any given time, whereby the self-blocking frequency ofsaid oscillator is determined by the reading of only one instrument, anda fixed resistance shunting said 5 impedance means once during onerevolution of said selecting switch, said fixed resistance identifyingthe order of connection of said instruments to said oscillator.

LEO S. CRAIG. LEON HILLMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,216,161 Curtiss et a1 Oct. 1,1940 2,347,160 Wallace April 18, 1944 2,347,345 Wallace April 25, 19442,333,248 Harvey Nov, 21, 1943 2,418,836 Hawes Apr. 15, 1947

